1. Field of the Invention
The invention relates to portable containers for delivering food products, such as pizzas, from a central location to one or more remote locations. More specifically, the invention relates to pizza delivery bags constructed to maintain internal atmospheric characteristics, such as temperature and humidity, at desired levels.
2. Description of Related Art
Bags for enclosing and transporting food items, such as pizza, are known in the art. These bags typically accommodate one or more food items to be delivered to a delivery site at a remote location. The food items are usually packaged, e.g., in cardboard boxes, before being inserted into the bag. The bags are used primarily to keep the food products warm while enroute from where they are prepared to the delivery site.
U.S. Pat. No. 6,018,143, issued Jan. 25, 2000 to Check, and incorporated herein by reference, discloses a portable, thermal bag for containing a food product, such as pizza. The bag has top and bottom panels and is closed along both sides at the rear end. The front end of the bag is open to permit insertion and removal of the food product. The top and bottom panels each have an outer cover layer, an inner cover layer, and electric resistance wires between the cover layers. The resistance wires may be plugged into the cigarette lighter of a delivery vehicle to keep the food product warm. A thermostat is placed at the center of the top panel to control the temperature. The bag has a quick release connector, which may also be plugged into a low voltage transformer in a restaurant where several bags may be kept before being used to carry a pizza in a delivery vehicle.
U.S. Pat. No. 5,892,202, issued Apr. 6, 1999 to Baldwin et al., and incorporated herein by reference, discloses a carrying case for storing and transporting heated articles. The carrying case includes a thermal storage assembly having a heat retention member and a heating coil assembly. The heat retention member absorbs and retains sensible heat and releases the sensible heat for an extended time period.
U.S. Pat. No. 5,880,435, issued Mar. 9, 1999 to Bostic, and incorporated herein by reference, discloses a food delivery container. The food delivery container includes a heating element with a phase change material, such as an ultra-high molecular weight polyethylene. The ultra-high molecular weight polyethylene transforms from a solid to a semi-solid at approximately 248-275.degree. F. The heating element includes a rigid envelope which is permeable to prevent gaseous build up during heating. The heating element, when placed within a suitable insulated container, will maintain food warm for several hours during storage or delivery. An electric resistance grid may be provided for supplying heat energy.
U.S. Pat. No. 5,676,051, issued Oct. 14, 1997 to Sinemus, and incorporated herein by reference, discloses a heated warming apparatus for food products. The apparatus includes one or a plurality of food containers, a housing, and a hot-air fan. The housing accommodates the food containers. The hot-air fan discharges air through a discharge opening in the housing. In order to maintain food products at a sufficiently high temperature, the hot air is heated extensively. However, the objective of reduced heating power expenditure is achieved by providing each food container with one or a plurality of inlet holes and one or a plurality of outlet holes. Each food container is arranged in the housing such that at least one of its holes is in fluid communication with the discharge opening.
U.S. Pat. No. 5,404,808, issued Apr. 11, 1995 to Smith et al., and incorporated herein by reference, discloses a carrier for hot food. In this carrier, a volume of dehumidifier material, such as calcium sulfate, is heated to a temperature greater than the pre-determined serving temperature of the food product and positioned in heat exchange relation with the food product, such that heat is transferred from the heated dehumidifier material to the food product and such that moisture is transferred from the food product to the dehumidifier material.
U.S. Pat. No. 5,078,050, issued Jan. 7, 1992 to Smith, and incorporated herein by reference, discloses a hot plate carrier. The carrier is disclosed as being for a partially baked dough product having a bottom crust and a moist topping. The carrier includes a vented container and a heater. The vented container contains the partially baked dough product. The heater is adapted to initially heat the bottom of the partially baked dough product to a temperature greater than 250.degree. F. to finish baking the crust of the dough product and maintain the temperature of the crust greater than the temperature of the moist topping. The vented container is formed to exhaust moist air from the interior of the container while maintaining the temperature of air adjacent to the moist topping on the dough product at above the dew point of air in the container to prevent moisture condensation and to draw air from outside the container to expel moisture from adjacent the bottom crust.
U.S. Pat. No. 4,806,736, issued Feb. 21, 1989 to Schirico, and incorporated herein by reference, discloses a heated delivery bag (portable container) for heating and storing pizza. The heated delivery bag includes a fabric box about 20 inches long, about 20 inches wide, and about 8 inches high. The box is supported in its four vertical corners by plexi-glass strips positioned inside sleeves. A lower rigid panel is located at the bottom of the fabric box. The lower rigid panel is used to support a heating unit. An upper rigid panel located above the heating units forms a compartment with the sides and top of the fabric box large enough to contain two pizzas in their delivery box containers. The heating unit includes an aluminum pan. The aluminum pan contains a block of insulation with a 1/2 inch depression on its upper surface. A silicone rubber heating element is positioned inside this depression. The temperature inside the portable container is maintained at between 165-180.degree. F. The portable container can be carried with one hand when used for delivering hot pizzas.
The devices referenced above generally are intended to transport food from a first location to a second location. However, devices according to the prior art are not believed to be constructed of materials that allow relative humidity within the bag to decrease in an optimal fashion or otherwise provide optimal humidity characteristics. Further, these devices suffer an inability to readily remove and/or replace heating elements associated therewith, e.g. during cleaning or in the event of heating element failure. Still further, none are believed to easily and inexpensively allow ready interchangeability of the heating elements, for use in more than one bag and/or in multiple locations. A need has arisen to address these and other problems.